1. Field of the Invention
The present invention relates generally to portable terminals such as cellular telephones, PCS (personal communication service) telephones, or PDA (personal digital assistant) telephones, and in particular, to a hinge device for such a portable terminal.
2. Description of the Related Art
FIG. 1 illustrates a portable terminal 100 according to a known art, showing in particular a foldable terminal. As shown in the drawing, the portable terminal 100 includes a body 110 and a folder 120. The body 110 is provided with an antenna device 111 on the top end and a battery 113 on the rear surface. On the surface facing the folder 120, the body 110 is typically provided with a transmission block (not shown) having a keypad and a microphone. The folder 120 is typically provided with a liquid crystal display (LCD), for displaying terminal status information and related data, and a receiving block (not shown) including a speaker device.
The folder 120 is combined with the body 110 to be rotatable by a hinge device, typically providing approximately 150 degrees of rotation for opening and closing. The same hinge device may be adopted equally to a portable terminal having a flippable or foldable folder.
FIG. 2 is a partial cross-sectional cut-away view showing a portion of a portable terminal adopting a conventional hinge device 200, and FIG. 3 is a disassembled perspective view of the hinge device 200 shown in FIG. 2. As shown in FIGS. 2 and 3, the hinge device 200 includes a hinge shaft 220 mounted inside a hinge housing 210, a hinge cam 230, a spring cap 240, and a hinge spring 250. The hinge device 200 is housed in a center hinge arm C1. The hinge shaft 220 is combined with a side hinge arm S1 of the body 110.
The hinge device 200 imparts sufficient biasing force to the folder 120 to cause the folder to open automatically, i.e. without applying additional force manually, when the folder is brought to an angle greater than a predetermined angle. At the same time, the hinge device 200 also imparts a biasing force causing the folder to close automatically when the folder is brought to an angle less than the same predetermined angle. This automatic opening and closing is achieved by the operation of the hinge spring 250, which provides the engaging force that causes the surface of an angular block 223 of the hinge shaft 220 to press against the surface of a concave block 231 of the hinge cam 230. Here, the predetermined angle is approximately 35 to 45 degrees.
One side of the hinge housing 210 is a semicircular, curved surface, and the other side is a planar surface, which facilitates assembly. The hinge housing 210 has a first open end 211 for receiving the hinge shaft 220. A guide groove 215 is formed in the planar surface of the hinge housing 210, extending longitudinally from the first open end 211. A pair of suspending grooves 217 are formed on either side of the hinge housing 210.
The hinge shaft 220 has at a D-shaped axis 221 formed at one end, with the angular block 223 being formed at the other. The D-shaped axis 221 has a recessed surface 225 formed on one side. The position of the recessed surface 225 on the D-shaped axis 221 with respect to the orientation of the angular block 223 determines the predetermined (i.e. opening/closing) angle of the folder 120. The axial length of the recessed surface 225 determines insertion depth of the hinge shaft 220 into the side hinge arm S1. The hinge shaft 220 is inserted into the hinge housing 210, with the D-shaped axis 221 projecting through a second open end 213.
The hinge cam 230 engages the angular block 223 of the hinge shaft 220, such that the concave block 231 meets and slides along the surface of the angular block 223. A pair of rises 233a and 233b are formed on either side of the concave block 231. The other end of the hinge cam 230 has a spring-fixing projection 235 and a hinge cam rib 237, which is inserted in the guide groove 215 of the hinge housing 210, enabling a rectilinear motion of the hinge cam 230 along the guide groove 215.
The spring cap 240 includes a pair of suspension jaws 241 to suspend the spring cap 240 in the suspending grooves 217 of the hinge housing 210, a cap rib 243 for inserting in the guide groove 215 of the hinge housing 210, and a fixing projection 245 to fix the spring cap 240 to the center hinge arm C1 of the folder 120.
The hinge spring 250 is installed between the hinge cam 230 and the spring cap 240 for pressing the hinge cam 230 firmly against the hinge shaft 220.
In the conventional hinge device of a portable terminal as described above, the numerous components of the hinge device have limited miniaturization. That is, the hinge shaft, hinge cam, and hinge spring are all housed within the hinge housing, and each component requires a minimum amount of space. Accordingly, further miniaturization of portable terminals adopting such a hinge device is hindered.